There is an ever-increasing demand for elastomers that are thermally stable at higher and higher temperatures as the automotive under-hood temperatures and wire and cable requirements increase dramatically. The search for new antioxidants is thus a compelling one to meet such needs.
Diphenylamine and diarylamine derivatives, hydroquinolines and certain mixtures of diphenylamine and mercaptotolylimidazole are considered the state of the art high temperature antioxidants for elastomers. Although such antioxidants have hitherto been the standards in the art, there has been a long felt need for still better high temperature antioxidants for elastomers especially as use temperatures continue to increase.
The instant substituted 1,4-diamino-2-butene compounds fall into three general groups depending on the various substituents on the two N-atoms.
When said substituents are alkyl, compounds having at least one lower alkyl, preferably two lower alkyl groups, on each N-atom are known. Lower alkyl includes methyl, ethyl, propyl butyl and amyl. Typical is N,N,N',N'-tetramethyl-2-butene-1,4-diamine. The use of such lower alkyl compounds as stabilizers is not disclosed. The instant alkyl substituents are higher alkali such as octyl, decyl, octadecyl and the like.
When said substituents are aralkyl, the hydrochloride salt of such the tetrabenzyl compound has a CAS number (5443-70-9), but no other published reference is known for said material nor is there any known utility for said compound. The other tetra-aralkyl compounds are believed to be novel materials. The stabilized compositions where the stabilizers are the instant compounds having one or more aralkyl substituents are not disclosed in the prior art.
When said substituents are aryl, British Patent No. 1,438,482 generically describes lubricant compositions containing substituted aryl amines of the formula R--X where R is a secondary amine residue containing two aromatic groups attached to nitrogen such as (Ar).sub.2 N--. This reference also generically describes compounds of the formula R--Y--R where Y is inter alia --CH.sub.2 CH.dbd.CHCH.sub.2 --. The only such compounds specifically disclosed by the British reference are those where R is an alkylated phenothiazine moiety. The closest compound of this reference is 1,4-but-2-ene-bis(3,7-dioctylphenothiazine).
British Patent No. 1,438,482 does not disclose or suggest that the compounds described therein can provide effective antioxidant protection to synthetic polymer compositions.